Get firmware updates after updating macOS

The installer downloads to your Applications folder and opens when it's complete. If it doesn't launch automatically, find Install macOS High Sierra in your Applications folder and double-click to open it.

Click Continue.

If your Mac needs a firmware update, you see this screen:

Follow the on-screen instructions to apply the firmware update.

Get firmware updates before reinstalling macOS

To reinstall macOS completely on Mac Pro (Mid 2010) and Mac Pro (Mid 2012), you need to run the installer twice: once to update the firmware, and a second time to reinstall macOS. Follow these steps:

The installer downloads to your Applications folder and opens when it's complete. If it doesn't launch automatically, find Install macOS High Sierra in your Applications folder and double-click to open it.

Click Continue.

If your Mac needs a firmware update, you see this screen:

Follow the on-screen instructions to apply the firmware update.

When the firmware update process completes and your Mac starts up, open Install macOS High Sierra again and follow the on-screen instructions to install macOS.